Aluminum alloy



3,252,841 ALUMINUM ALLOY George S. Foerster, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed Sept. 25, 1964, Ser. No. 399,360

3 Claims. (Cl. 148-325) This application is a continuation-in-p-art of patent application Serial No. 182,649, filed March 26, 1962, now abandoned.

- This invention relates to aluminum alloys and more particularly is concerned with a novel aluminum base magnesium-silicon alloy containing additive metals in predetermined quantities which provide a specific relationship between silicon and the additive metal and to a high strength extruded product prepared thereby.

In general, the novel aluminum base alloy of the present invention contains on a weight basis from about 0.5 to about 2 percent magnesium, from about 0.5 to about 10,percent silicon, from about 0.5 to about 20 percent of an additive metal selected from the group consisting of calcium, strontium, barium, rare earth, thorium and mixtures thereof, balance aluminum, and being further characterized in that the silicon and additive metal are maintained within a specific predetermined ratio and the silicon content is about equal to or in excess of that neededfor formation of magnesium silicide (Mg Si).

By maintaining these specific relationships between the concentrations of alloying ingredient and silicon in the present novel alloy, I have discovered that unexpectedly high tensile strengths are realized in extruded prod ucts prepared therefrom. The alloy is particularly suited for the preparation of pellet extrusions which exhibit excellent and unusually high tensile strength in the extruded, solution heat treated, quenched and aged condition. The excellent strength characteristics -of the extruded products prepared from the present novel alloy having these well-defined and requisite interrelationships of alloying component concentrations are not predictable nor anticipated from the known art.

To illustrate; Wood et al. (U.S. 1,932,836) alleges an aluminum base' casting alloy having high fluidity and good general casting properties in the molten state. This alloy contains 1 to 8 percent magnesium, 0.5 to 6 percent zinc and 0.01 to 2 percent calcium, the balance being substantially aluminum. This patent suggests that other alloying elements such as manganese, nickel, copper, silicon, etc. in undetermined amounts may be added in some instances. This patented alloy which must contain zinc (excluded from the present novel 'alloy) and suggests the use of silicon only as an optional additive to be used, if at all, in some undetermined amount is not pertinent. (Silicon in a controlled, predetermined concentration is an essential component of the present novel alloy.)

French patent (975,591) alleges an aluminum base alloy containing magnesium to which manganese can be added and which also contains calcium. This alloy, as is set forth in the patent, contains up to 1 percent iron, up to 1 percent silicon, up to 1 percent manganese, from 1 to 13 percent magnesium and from 0.1 to 3' percent calcium. No criticality of ratio and concentration of silicon-magnesium-additive metal is indicated in this patent. In fact, the range covered by the French patent cannot meet the requisite alloy ingredient interrelationship needed for operability in the present novel all-0y.

Ordinarily, barium, calcium and cerium are employed as additive metals in the present novel alloy. The actual amount of additive to be employed in the alloy is varied within the disclosed range in accordance with the properties and characteristics, e.g. density, etc., desired in the extruded product. The actual silicon content employed in the alloy, within the range of from 0.5 to 10 percent as set forth hereinbefore, is established and maintained in accordance with the equation:

: Wt. percent Mg.

Wt. percent Si 1 73 +K (weight percent additive member) Minimum values for K to be used with the preferred additive metals to assure the incorporation of the requisite amount of silicon into the alloy are barium (0.1),

calcium 1.0) and cerium, (added as misch metal) (0.1).

TABLE I Concentration in Alloy (weight percent) Metal Operable Preferred Range Range 1 Added as misch metal.

If it is desired to employ thorium, strontium, or other termining silicon level is the atomic percent equivalent of the concentration levels shown hereinabove for barium, calcium or cerium.

The additive members can be used alone in the alloy or a mixture of additives can be employed. With mixtures of additive metals the concentration of each of the individual members used therein is proportionally reduced so that the total concentration of the additive in the alloy falls within the range and in accordance with the relationships set forth hereinbefore.

The alloy is prepared using foundry alloying and melt techniques as practiced in the aluminum art.

This alloy is suited for use both with ingot and pellet extrusion processes and as set forth hereinbefore is particularly suitable for fabricating high strength pellet extrusions. For the two types of extrusion operations, a melt of the alloy is solidified into ingots, or preferably more rapidly quenched as by atomizing into pellets. Conveniently pellets can be produced by jet atomizing or'wheel atomizing either in an inert atmosphere such as natural gas, nitrogen, argon, etc. for example, or in air.

The billet or atomized pellets are fabricated into extrusions using normal billet or pellet extrusion techniques and apparatus.

For use in the pellet extrusion process, ordinarily the pellets are preheated to a temperature at least that of the extruder container and the heated pellets then are loaded into the container and extruded. However, if desired, the pellets can be used in the extrusion process Without preheating. Also, the pellets can be precompacted prior to extrusion. By precompacting the pellets In a manner similar to that shown by the foregoing examples, alloys can be prepared containing:

under reduced pressure, blistering and formation of in- A1 1'4Mg 9-2Si 6ca (K214) ternal voids substantially are avoided during any post extrusion heat treatment that may be employed. A 1-4Mg -9S1T1Ce The so-extruded product ordinarily is solution heat A1 1-4Mg 2-8S} 2OO5 treated, quenched and aged thereby providing a final A1*1'4Mg 1'8S{5Ce (KZO-Z) product exhibiting unexpectedly high tensile strength. Al41-4Mg 2'8S110Ce (KZOJ) this treatment K F P the 1ength 0f time for Solu These alloys readily can be fabricated into ingots or l heat treatment is mmlmlzed to ,aveld (1) agglemera pellets and subsequently extruded into fabricated form. non of any dlepersed phase that f t Present m the Various modifications can be made in the present iny, TeCOVeTY, recrystal-hzatlon and (4) vention without departing from the spirit or scope theregg n h t f of for it is understood that I limit myself only as defined m strength extrusions and particularly pellet extrusions un- 1. A high Strength aluminum alloy pellet extrusion expectedly be produced at relatlvely extruslon consisting essentially of from about 0.5 to about 2 weight i' from about 750 to about 29 percent magnesium, from about 0.5 to about 10 weight t Increase the Strength of the extruslen results by percent silicon, an additive metal, and remainder alumig qgenchglg t extruded Preduet as 1t emerges num, said additive metal being a member selected from mm t e 1e an agmg the group consisting of barium calcium and cerium said g z fg z g if 1 3:2 3: gg fgf fi l i fi g i alloy being further characterized in that the concentrae 1 15 In an tion of said additive metal and the actual weight perlurg t it tlliereto. 1 T 1 cent of silicon in said alloy are predetermined in accordas misch metal) as an additive member was prepared. t t M One portion of the alloy was atomized into pellets, about a Wt ercent Percen O 1 wt 85% of which ranged from -20 +200 mesh, U.S. p 1-73 Standard Sieve, balance passing through the 200 mesh Percent banum) sieve. A second portion of the alloy was cast into a 3 wt. percent Mg. inch diameter ingot. (b) wt. percent S1 +1.0 (0.75-6 wt.

The two forms of the alloy were extruded as follows. 40 percent calcium) For the pellet extrusion, a batch of the pellets was I preheated to about 700 F. and placed in the pellet con- (0) Wt percent Percent (l 2O Wt tainer of a ram extruder which container also Was about this same temperature. r P cenum) For ingot extrusion, billets about 4 inches long were 40 cut from'the cast ingot. said extrusion being in the extruded, solution heat treat- The pellets and billets both were extruded at an exed, quenched and aged condition and characterized by trusion temperature of about 800 F. and an extrusion an unexpectedly high tensile strength. rate of about 5 feet per minute into a strip 0.2 inch thick 2. A high strength aluminum alloy pellet extrusion by 1 inch wide. The resulting strip then was solution 50 consisting essentially of from about 0.5 to about 2 weight heat treated at about 970 F. for /2 hour, quenched and percent magnesium, from about 0.5 to about 10 weight aged 16 hours at 320 F. percent silicon, an additive metal, and remainder alurni- Standard test bars were prepared and the percent elonnum, said additive metal being a member selected from gation, tensile yield strength and tensile strength of the r, the group consisting of barium, calcium and cerium, said alloys determined at room temperature. The results of alloy being further characterized in that the concentrathese tests are presented in Table II which follows. tion of said additive metal and the actual weight per- TABLE II Test Results Run No. Alloy i t g e l eiri are Perlczent L000 TYS Ts Ingot Extrusion:

1 Al-1.2 Mg1.55 si4 Ba 0.2 s 41 A11.2Mg-2.3 si4 Ba 0.4 7 42 47 Al1.2 Mg3.5 Si-2 Ca 1. 4 4 42 4e Al1.2 Mg1.7 sr-s Ge 0. 2 s 39 45 Al-1.2Mg-2.7 Si5 Ce 0.4 s 47 51 All.5 Mg-4 Si-Z Ca 1. 0 4 56 1 Added as misch metal.

cent of silicon in said alloy are predetermined in accordance with the following relationship:

(a) wt. percent SEW-M2 (3-6 wt.

percent barium) Wt. percent Mg.

(b) wt. percent Si; 1 73 +1.4 (24 Wt.

percent calcium) 0) Wt. ercent sii kOfi (510 Wt.

1.73 percent cerium) said extrusion being in the extruded, solution heat treated, quenched and aged condition and characterized by an unexpectedly high tensile strength.

3. A high strength aluminum alloy pellet extrusion consisting essentially of about 1.5 weight percent magnesium, about 2 weight percent calcium, about 4 weight percent silicon, balance aluminum, said extrusion being in the extruded, solution heat treated, and aged condition and, characterized as having a minimum tensile yield 5 strength of about 50,000 p.s.i.

References Cited by the Examiner UNITED STATES PATENTS 1,932,836 10/1933 Wood etal 7s 147 3,031,299 4/1962 Criner 75-147 3,113,052 12/1963 Schneck 148-115 3,147,110 9/1964 Foerster 14811.5 X

If DAVID L. RECK, Primary Examiner. 0 C. N. LOVELL, Assistant Examiner. 

1. A HIGH STRENGTH ALUMINUM ALLOY PELLET EXTRUSION CONSISTING ESSENTIALLY OF FROM ABOUT 0.5 TO ABOUT 2 WEIGHT PERCENT MAGNESIUM, FROM ABOUT 0.5 TO ABOUT 10 WEIGHT PERCENT SILICON, AN ADDITIVE METAL, AND REMAINDER ALUMINUM, SAID ADDITIVE METAL BEING A MEMBER SELECTED FROM THE GROUP CONSISTING OF BARIUM, CALCIUM AND CERIUM, SAID ALLOY BEING FURTHER CHARACTERIZED IN THAT THE CONCENTRATION OF SAID ADDITIVE METAL AND THE ACTUAL WEIGHT PERCENT OF SILICON IN SAID ALLOY ARE PREDETERMINED IN ACCORDANCE WITH THE FOLLOWING RELATIONSHIP: (A) WT. % SI >= (WT. % MG/1.73) + 0.1(1 - 10 WT. % BA) (B) WT. % SI >= (WT. % MG/1.73) + 1.0(0.75 - 6 WT. % CA) (C) WT. % SI >= (WT. % MG/1.73) + 0.1(1 - 20 WT. % CE) SAID EXTRUSION BEING IN THE EXTRUDED, SOLUTION HEAT TREATED, QUENCHED AND AGED CONDITION AND CHARACTERIZED BY AN UNEXPECTEDLY HIGH TENSILE STRENGTH. 